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Network Infrastructure

Figure 1 shows the CORD network infrastructure. The underlay fabric at the heart of the implementation is responsible for interconnecting all parts of CORD, including access I/O blades, compute nodes (servers), and upstream routers. In addition, the fabric control application that runs on ONOS interacts with a number of other applications to provide CORD services.

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Figure 1. CORD Architecture.

In the current implementation, there are actually two sets of ONOS controllers with different responsibilities. The first ONOS cluster (onos-cord) is responsible for the overlay infrastructure (virtual networking and service composition) and the access infrastructure. This cluster hosts the VTN and vOLT applications, respectively.

The second ONOS cluster (onos-fabric) is responsible for controlling the fabric and interfacing with conventional upstream routers. This cluster hosts the Fabric Control and vRouter applications, respectively.

Multicast control is via two additional applications, IGMP snooping and PIM-SSM, where the former runs on onos-cord and the latter runs on onos-fabric. (For simplicity, we show only a single Multicast Control application in Figure 1.)

In principle, all the applications could run on a single ONOS cluster. We chose to split responsibilities to have better isolation and separation of concerns, which was especially helpful during development. However, to simplify the exposition and diagrams, we show all the applications running on a single ONOS cluster in Figure 1.

For more information about each sub-system of the network infrastructure, see the following related pages:



Welcome to the Trellis wiki space. All information on this wiki is publicly accessible. If you would like to contribute to this space, you will need a CORD account:

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Trellis is an open-source multi-purpose L2/L3 leaf-spine switching fabric. The development of Trellis over the last four years has been influenced by three core trends in the networking industry:

  • First, Trellis is built using bare-metal switches with merchant-silicon ASICs. Instead of using OEM networking hardware, Trellis uses hardware directly from ODMs. The trend of using bare-metal (white-box) switches is unmistakable in the networking industry today, spurred by the massive bandwidth-density and growing sophistication of merchant silicon ASICs. Production quality Trellis today is based on EdgeCore switches with Broadcom Trident2, Tomahawk and Qumran switch ASICs. The Trellis team continues to work towards including more ODMs and merchant silicon vendors.
  • Second, Trellis is based on SDN principles, to provide simpler, more flexible and easily customizable networks. By externalizing the network’s control, management functions and policy decisions in the ONOS SDN controller, Trellis provides network operators with a number of SDN benefits compared to traditional box-embedded network control. These include centralized configuration, automation, operation and troubleshooting.
  • Third, Trellis is open-source. The networking industry has seen an explosion of open source projects, and network operators have been eager to embrace open-source solutions. Trellis allows operators unparalleled ability to customize Trellis for their application, integrate with the rest of their systems, add features and APIs themselves and not be beholden to a traditional vendor’s timelines and prices. An absence of commercial licenses lowers the bar for anyone to try out Trellis.

Together, all three attributes of Trellis considerably lower the Total Cost of Ownership (TCO) for operators who plan to run it in production.


You can learn more about Trellis features and design concepts by visiting the Project Website and reading the Platform Brief.


  • Classic-SDN Control with ONOS to directly program ASIC forwarding tables in bare metal switches with merchant silicon
  • L2 forwarding (Bridging) within server-racks and L3 forwarding (Routing) across racks
  • MPLS Segment routing for better scale and reduced programming
  • Control plane functionality with Trellis vRouter for external connectivity
  • N-way redundancy and tier-1 telecom operator scale
  • Support for different use cases ranging from Central Office to backhaul in operator networks
  • Single-pane-of-glass monitoring and troubleshooting with ONOS
  • CapEx and OpEx savings with white-box hardware and open source software
  • Future Proof: P4 and Stratum integration to unlock advanced capabilities

Use Cases

Distributed Fabric for Access/Edge Networking

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Disaggregated BNG in SEBA using P4

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Enterprise Datacenter Fabrics

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Chassis Routers

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Key People & Communication Channels

Charles Chan & Pier Luigi Ventre are the ONF Ambassadors for Trellis. For any questions regarding joining the Trellis platform as a contributor or getting onboarded, please reach out via the following channels:

If you're not able to get your question answered via the above channels, feel free to send an email with a link to your question via the mailing list or Slack to


Interested in more information or want to get involved? Reach out to the Trellis Developer Mailing List.

We expect all ONF employees, member companies, and participants to abide by our Code of Conduct. If you have any questions or concerns, please notify a member of the ONF team or email


Having trouble getting started? First, reach out to the mailing list or Slack team. If you still have questions or concerns, please email